Linux Kernel Architecture

Mauerer's book << Linux kernel Architecture >> is clear and you can trace the flow of the source code.
I make this comment since I have painful experience in reading << Understanding the Linux kernel >>.

The Understanding series is quite hard to me.

If you really have passion in the linux kernel, I would suggest you first read Robert Love 's << Linux Kernel Development >> .

The linux source code is Overwhelming. But once you can ...

Linux kernel e-book :
http://www.kernelchina.org/?q=node/69